It might not have been luck. Alec may have sensed that the lines didn’t ring true. Lucas may have shared his desire to film more with him. There is a lot we don’t know and we unfortunately can’t ask Alec. But I would say that whatever he did there was likely his own take on it. As a stand alone film you can either take it as hesitation from apprehension in telling Luke about it or hesitation from coming close to the truth but not exactly. Not matter how it happened, it really makes the scene resonate with the “certain point of view” we later find out it is.